Best way to cut the shoulder

[Bill Carey]

I'm making a table with slightly curved legs and the apron needs to have slightly curved shoulders to make a tight joint. It looks straight in the pic but it has a camber to it.

2021-08-28_21h35_24.jpg

How would you cut the shoulder? I'm thinking a flush cut router bit with a top bearing and use the leg itself as the pattern after inserting the tenon part way. Other suggestions? Thx.

[Derek Cohen]

Bill, keep everything square/rectangular and cut the mortice-and-tenon. Once you have the fit you desire, only then mark and cut the curved sections.

Regards from Perth

Derek

[Malcolm McLeod]

I used Dominos to join a recent project with (shallow) curved joints - - I used Dr. Cohen's strategy of keeping the joint square until the mortice was cut, and mortices were cut 'deep' to allow for later material removal as the curves were established. Once the curves got cut, I measured for final depth of mortice, and adjusted the floating tenon length to match.

As for the curves, keep in mind the radius of travel of the bit :: inside and outside are different (there was quite a contentious SMC-debate recently on this). As I understand your description, the bit will register on the radius of the leg, and so cut the shoulder radius larger (=leg radius + bit diameter). On a very shallow curve (large radius), you might get an acceptable fit - maybe with a little bit of extra grunt on the clamps? As the radius tightens, the percentage added by the bit gets more dramatic. Judging from previous examples of your work, I suspect you will not be satisfied with this method.

I addressed this radius issue by making a template for the 'shoulder' curve, and used a pattern bit to transfer this shape to the final component. Then I laid this template on a second mating template, scribed a line, and carefully cut/planed/sanded until the second template fit precisely on the first. Then the second template was used to transfer this curve to it's final component. Tedious. But tight joints.

I don't remember the source, but somewhere saw/read/heard a Pro woodworker basically say that if a commission piece had a curve in it, they wouldn't make any money. After my foray into the above 'Land of Sinuosity', I know what they mean. Good thing my hourly rate is low!

[Joe Calhoon]

I cut curve shoulders on door tenons using the shaper and the end of the tenon as a guide. I think the same principle could be used with a router. These are short tenons only about 1 1/2” long. I use the curve of the rail to lay out the end of the mullion. I needed to add pieces on each side of the mullion but still quicker than making a jig.
You can see the process here.
https://www.instagram.com/p/CDKJc1Tj...dium=copy_link

[Brian Holcombe]

Similar to Joe, I cut the end of the tenon at the desired angle, then use the tablesaw fence as a guide for cutting the shoulders.

[Bill Carey]

Derek - yes. I learned that lesson, and the tuition was only 3 or 4 bf of QSWO and several hours. Relativley cheap when it comes to hard knocks education.

Malcolm - I read that thread and it was worrying me, so I'm gonna do a test with loose tenons and see how that works.

Joe and Brian - interesting idea. Along with the loose tenon test, I'm going to make a template that fits the curve of the leg, and use that as a guide for routing the curved shoulder.

This is basically what I need:
2021-08-29_09h49_24.jpg

If I make that template I can use it with a shallow flush bit to cut the shoulder. Should be a fun day in the shop today.

[Brian Holcombe]

Bill, sorry I would not do a curved shoulder on the tablesaw, I was going by your diagram. Disregard.

I would do that on the router as you are planning.

[Bill Carey]

Bill, sorry I would not do a curved shoulder on the tablesaw, I was going by your diagram. Disregard.

I would do that on the router as you are planning.

Ya, the first pic looked like straight cuts. When I made the end tables with the 3 degree legs I used the table saw with a cast iron tenon jig - once I dialed it in it worked great.

[Bill Carey]

So the router idea worked pretty well. Made a template that fit nicely and used a top bearing bit (same one I use to route dovetails) and it fit great off the router. But the jig I made didn't allow for easy registration for the back shoulder, so that needs some thought.
20210829_140520.jpg

But I think I will need to make a template for each leg. Which is a PITA - sanding and fitting, sanding and fitting, etc. - took much longer than routing the apron piece. Dunno. The leg is so close to flat at the top I may tweak the design and leave a flat for the apron to land on.